Alignment fixing on a data protection system during continuous data replication to deduplicated storage

ABSTRACT

The system, process, and methods herein describe a mechanism for aligning IOs with block sizes. The alignment may occur on a data protection appliance as part of a continuous replication process. The IO offset may be rounded down, and the size may be rounded up, so that each is a multiple of the block size.

A portion of the disclosure of this patent document may contain commandformats and other computer language listings, all of which are subjectto copyright protection. The copyright owner has no objection to thefacsimile reproduction by anyone of the patent document or the patentdisclosure, as it appears in the Patent and Trademark Office patent fileor records, but otherwise reserves all copyright rights whatsoever.

TECHNICAL FIELD

This invention relates generally to data backups, and more particularlyto continuous data replication on deduplicated storage.

CROSS REFERENCE TO RELATED FILINGS

This application is related to co-pending U.S. patent application Ser.No. 14/227,208 for SYNTHESIZING VIRTUAL MACHINE DISK BACKUPS, U.S.patent application Ser. No. 14/225,089 for RECOVERING CORRUPT VIRTUALMACHINE DISKS, and U.S. patent application Ser. No. 14/225,069 forALIGNMENT FIXING ON A STORAGE SYSTEM DURING CONTINUOUS DATA REPLICATIONTO DEDUPLICATED STORAGE, all filed concurrently herewith andincorporated by reference for all purposes.

This application is related to co-pending U.S. patent application Ser.No. 14/108,002 for INITIALIZING BACKUP SNAPSHOTS ON DEDUPLICATEDSTORAGE, U.S. patent application Ser. No. 14/108,021 for MAINTAININGBACKUP SNAPSHOT ON DEDUPLICATED STORAGE USING CONTINUOUS REPLICATION,U.S. patent application Ser. No. 14/108,032 for POINT-IN-TIME RECOVERYON DEDUPLICATED STORAGE, U.S. patent application Ser. No. 14/108,053 forMAINTAINING POINT-IN-TIME GRANULARITY FOR BACKUP SNAPSHOTS, U.S. patentapplication Ser. No. 14/108,060 for MAINTAINING BACKUP SNAPSHOTS USINGCONTINUOUS REPLICATION FOR MULTIPLE SOURCES, and U.S. patent applicationSer. No. 14/108,072 for RECOVERING CORRUPT STORAGE SYSTEMS, all herebyincorporated by reference for all purposes.

BACKGROUND

Computer data is vital to today's organizations, and a significant partof protection against disasters is focused on data protection. Assolid-state memory has advanced to the point where cost of memory hasbecome a relatively insignificant factor, organizations can afford tooperate with systems that store and process terabytes of data.

Conventional data protection systems include backup drives for storingorganizational production site data on a periodic basis. Such systemssuffer from several drawbacks. First, they may require a system shutdownduring backup since the data being backed up cannot be used during thebackup operation. Second, they limit the points in time to which theproduction site can recover. For example, if data is backed up on adaily basis, there may be several hours of lost data in the event of adisaster. Third, the data recovery process itself may take a long time.

Another conventional data protection system uses data replication, bycreating a copy of the organization's production site data on asecondary backup storage system, and updating the backup with changes.The backup storage system may be situated in the same physical locationas the production storage system, or in a physically remote location.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features, and advantages of embodiments disclosed herein may bebetter understood by referring to the following description inconjunction with the accompanying drawings. The drawings are not meantto limit the scope of the claims included herewith. For clarity, notevery element may be labeled in every figure. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingembodiments, principles, and concepts. Thus, features and advantages ofthe present disclosure will become more apparent from the followingdetailed description of exemplary embodiments thereof taken inconjunction with the accompanying drawings in which:

FIG. 1 is a simplified illustration of a data protection system, inaccordance with an embodiment of the present disclosure;

FIG. 2 is a simplified illustration of a write transaction for ajournal, in accordance with an embodiment of the present disclosure;

FIG. 3 is a system for initializing a backup snapshot, consistent withan embodiment of the present disclosure;

FIG. 4 is a system for synthesizing new backup snapshots, consistentwith an embodiment of the present disclosure;

FIG. 5 depicts a process for byte alignment on a storage devicesconsistent with an embodiment on the present disclosure;

FIG. 6 depicts a process for asynchronously aligning IOs consistent withan embodiment of the present disclosure;

FIG. 7 depicts a method for identifying dirty IOs consistent with anembodiment of the present disclosure; and

FIG. 8 depicts a general purpose computer system, consistent with anembodiment of the present disclosure.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. While the invention is described inconjunction with such embodiment(s), it should be understood that theinvention is not limited to any one embodiment. On the contrary, thescope of the invention is limited only by the claims and the inventionencompasses numerous alternatives, modifications, and equivalents. Forthe purpose of example, numerous specific details are set forth in thefollowing description in order to provide a thorough understanding ofthe present invention. These details are provided for the purpose ofexample, and the present invention may be practiced according to theclaims without some or all of these specific details. For the purpose ofclarity, technical material that is known in the technical fieldsrelated to the invention has not been described in detail so that thepresent invention is not unnecessarily obscured.

It should be appreciated that the present invention can be implementedin numerous ways, including as a process, an apparatus, a system, adevice, a method, or a computer readable medium such as a computerreadable storage medium or a computer network wherein computer programinstructions are sent over optical or electronic communication links.Applications may take the form of software executing on a generalpurpose computer or be hardwired or hard coded in hardware. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention.

An embodiment of the invention will be described with reference to adata storage system in the form of a storage system configured to storefiles, but it should be understood that the principles of the inventionare not limited to this configuration. Rather, they are applicable toany system capable of storing and handling various types of objects, inanalog, digital, or other form. Although terms such as document, file,object, etc. may be used by way of example, the principles of theinvention are not limited to any particular form of representing andstoring data or other information; rather, they are equally applicableto any object capable of representing information.

Systems, processes, and methods are discussed herein for enablingcontinuous data backups to deduplicated storage. In some embodiments, aninitial backup snapshot of a source storage system may be created on thededuplicated storage using a data protection appliance. As changes aremade to the source storage system, the IO's may be continuouslycommunicated to the deduplicated storage for backup and protection.

In some embodiments, the deduplicated storage and/or data protectionappliance may maintain journals, including data journals and metadatajournals, for synthesizing new backup snapshots and/or recovering files.The journals may include DO and UNDO information compiled from IO'scommunicated from the data protection appliance to the deduplicatedstorage. These IO's may be applied to a backup snapshot to restore thesnapshot to a previous point-in-time, or may be used to synthesize a newsnapshot.

In an embodiment, data protection windows may be defined based on policyor user preference. The data protection windows may be used to maintainsnapshots and/or journals for designated periods of time. For example,short-term windows may maintain both snapshots and journals for anypoint-in-time recovery (assuming the point-in-time falls within theshort-term window). Mid-term windows, in contrast, may delete journalsbut maintain all the snapshots created during a period, and long-termwindows may delete all the journals and select snapshots. Definingdifferent protection windows may allow point-in-time recovery for filesaccessed recently, while also providing reduced storage consumption forlong-term backups.

The systems discussed herein may additionally allow backup snapshots tobe synthesized on deduplicated storage from IO's provided from multipledata protection appliance. For example, two data protection appliancesmay protect a single SAN. Each of those data protection agents mayreport IO's to the deduplicated storage, and a single backup snapshotmay be synthesized from the journals maintaining those IO's.

The following non-limiting definitions may be helpful in understandingthe specification and claims:

BACKUP SITE—may be a facility where replicated production site data isstored; the backup site may be located in a remote site or at the samelocation as the production site; a backup site may be a virtual orphysical site.

CDP—Continuous Data Protection, may refer to a full replica of a volumeor a set of volumes along with a journal which allows any point in timeaccess, the CDP copy is at the same site, and maybe the same storagearray of the production site.

DATA PROTECTION APPLIANCE (“DPA”)—may be a computer or a cluster ofcomputers, or a set of processes that serve as a data protectionappliance, responsible for data protection services including inter aliadata replication of a storage system, and journaling of I/O requestsissued by a host computer to the storage system. The DPA may be aphysical device, a virtual device running, or may be a combination of avirtual and physical device.

HOST—may be at least one computer or networks of computers that runs atleast one data processing application that issues I/O requests to one ormore storage systems; a host is an initiator with a SAN; a host may be avirtual machine.

HOST DEVICE—may be an internal interface in a host to a logical storageunit.

IMAGE—may be a copy of a logical storage unit at a specificpoint-in-time.

INITIATOR—may be a node in a SAN that issues I/O requests.

I/O—may mean a input, output, read, read request, write, write request,or any combination thereof.

JOURNAL—may be a record of write transactions issued to a storagesystem. A journal may be used to maintain a duplicate storage system,and to rollback the duplicate storage system to a previouspoint-in-time.

LOGICAL UNIT—may be a logical entity provided by a storage system foraccessing data from the storage system.

LUN—may be a logical unit number for identifying a logical unit. Mayalso refer to one or more virtual disks or virtual LUNs, which maycorrespond to one or more Virtual Machines. As used herein, LUN and LUmay be used interchangeably to refer to a LU.

PHYSICAL STORAGE UNIT—may be a physical entity, such as a disk or anarray of disks, for storing data in storage locations that can beaccessed by address.

PRODUCTION SITE—may be a facility where one or more host computers rundata processing applications that write data to a storage system andread data from the storage system; may be a virtual or physical site.

RPA—may be replication protection appliance, and is another name forDPA. An RPA may be a virtual DPA or a physical DPA.

SAN—may be a storage area network of nodes that send and receive I/O andother requests, each node in the network being an initiator or a target,or both an initiator and a target.

SOURCE SIDE—may be a transmitter of data within a data replicationworkflow. During normal operation a production site is the source side,and during data recovery a backup site is the source side. Source sidemay be a virtual or physical site.

SNAPSHOT—a snapshot may refer to an image or differentialrepresentations of an image, i.e. the snapshot may have pointers to theoriginal volume, and may point to log volumes for changed locations.Snapshots may be combined into a snapshot array, which may representdifferent images over a time period.

SPLITTER/PROTECTION AGENT—may be an agent running either on a productionhost a switch or a storage array which can intercept IO and split themto a DPA and to the storage array, fail IO redirect IO or do any othermanipulation to the IO; the splitter or protection agent may be used inboth physical and virtual systems. The splitter may be in the IO stackof a system and may be located in the hypervisor for virtual machines.May be referred to herein as an Open Replicator Splitter (ORS).

STORAGE SYSTEM—may be a SAN entity that provides multiple logical unitsfor access by multiple SAN initiators.

STREAMING—may mean transmitting data in real time, from a source to adestination, as the data is read or created.

SYNTHESIZE—may mean creating a new file using pointers from existingfiles, without actually copying the referenced data. For example, a newfile representing a volume at a points-in-time may be created usingpointers to a file representing a previous point-in-time, as wellpointers to journal representing changes to the volume.

TARGET—may be a node in a SAN that replies to I/O requests.

TARGET SIDE—may be a receiver of data within a data replicationworkflow; during normal operation a back site is the target side, andduring data recovery a production site is the target side; may be avirtual or physical site.

VIRTUAL VOLUME—may be a volume which is exposed to host by avirtualization layer, the virtual volume may be spanned across more thanone site and or volumes.

VIRTUAL RPA (vRPA)/VIRTUAL DPA (vDPA)—may be an DPA running in a VM.

WAN—may be a wide area network that connects local networks and enablesthem to communicate with one another, such as the Internet.

Overview of a Backup System Using a Journaling Process

Reference is now made to FIG. 1, which is a simplified illustration of adata protection system 100, in accordance with an embodiment of thepresent invention. Shown in FIG. 1 are two sites; Site I, which is aproduction site, on the right, and Site II, which is a backup site, onthe left. Under normal operation the production site is the source sideof system 100, and the backup site is the target side of the system. Thebackup site is responsible for replicating production site data.Additionally, the backup site enables rollback of Site I data to anearlier pointing time, which may be used in the event of data corruptionof a disaster, or alternatively in order to view or to access data froman earlier point in time.

During normal operations, the direction of replicate data flow goes fromsource side to target side. It is possible, however, for a user toreverse the direction of replicate data flow, in which case Site Istarts to behave as a target backup site, and Site II starts to behaveas a source production site. Such change of replication direction isreferred to as a “failover”. A failover may be performed in the event ofa disaster at the production site, or for other reasons. In some dataarchitectures, Site I or Site II behaves as a production site for aportion of stored data, and behaves simultaneously as a backup site foranother portion of stored data. In some data architectures, a portion ofstored data is replicated to a backup site, and another portion is not.

The production site and the backup site may be remote from one another,or they may both be situated at a common site, local to one another.Local data protection has the advantage of minimizing data lag betweentarget and source, and remote data protection has the advantage is beingrobust in the event that a disaster occurs at the source side.

The source and target sides communicate via a wide area network (WAN)128, although other types of networks are also adaptable for use withthe present invention.

In accordance with an embodiment of the present invention, each side ofsystem 100 includes three major components coupled via a storage areanetwork (SAN); namely, (i) a storage system, (ii) a host computer, and(iii) a data protection appliance (DPA). Specifically with reference toFIG. 1, the source side SAN includes a source host computer 104, asource storage system 108, and a source DPA 112. Similarly, the targetside SAN includes a target host computer 116, a target storage system120, and a target DPA 124.

Generally, a SAN includes one or more devices, referred to as “nodes”. Anode in a SAN may be an “initiator” or a “target”, or both. An initiatornode is a device that is able to initiate requests to one or more otherdevices; and a target node is a device that is able to reply torequests, such as SCSI commands, sent by an initiator node. A SAN mayalso include network switches, such as fiber channel switches. Thecommunication links between each host computer and its correspondingstorage system may be any appropriate medium suitable for data transfer,such as fiber communication channel links.

In an embodiment of the present invention, the host communicates withits corresponding storage system using small computer system interface(SCSI) commands.

System 100 includes source storage system 108 and target storage system120. Each storage system includes physical storage units for storingdata, such as disks or arrays of disks. Typically, storage systems 108and 120 are target nodes. In order to enable initiators to send requeststo storage system 108, storage system 108 exposes one or more logicalunits (LU) to which commands are issued. Thus, storage systems 108 and120 are SAN entities that provide multiple logical units for access bymultiple SAN initiators.

Logical units are a logical entity provided by a storage system, foraccessing data stored in the storage system. A logical unit isidentified by a unique logical unit number (LUN). In an embodiment ofthe present invention, storage system 108 exposes a logical unit 136,designated as LU A, and storage system 120 exposes a logical unit 156,designated as LU B.

In an embodiment of the present invention, LU B is used for replicatingLU A. As such, LU B is generated as a copy of LU A. In one embodiment,LU B is configured so that its size is identical to the size of LU A.Thus for LU A, storage system 120 serves as a backup for source sidestorage system 108. Alternatively, as mentioned hereinabove, somelogical units of storage system 120 may be used to back up logical unitsof storage system 108, and other logical units of storage system 120 maybe used for other purposes. Moreover, in certain embodiments of thepresent invention, there is symmetric replication whereby some logicalunits of storage system 108 are used for replicating logical units ofstorage system 120, and other logical units of storage system 120 areused for replicating other logical units of storage system 108.

System 100 includes a source side host computer 104 and a target sidehost computer 116. A host computer may be one computer, or a pluralityof computers, or a network of distributed computers, each computer mayinclude inter alia a conventional CPU, volatile and non-volatile memory,a data bus, an I/O interface, a display interface and a networkinterface. Generally a host computer runs at least one data processingapplication, such as a database application and an e-mail server.

Generally, an operating system of a host computer creates a host devicefor each logical unit exposed by a storage system in the host computerSAN. A host device is a logical entity in a host computer, through whicha host computer may access a logical unit. In an embodiment of thepresent invention, host device 104 identifies LU A and generates acorresponding host device 140, designated as Device A, through which itcan access LU A. Similarly, host computer 116 identifies LU B andgenerates a corresponding device 160, designated as Device B.

In an embodiment of the present invention, in the course of continuousoperation, host computer 104 is a SAN initiator that issues I/O requests(write/read operations) through host device 140 to LU A using, forexample, SCSI commands. Such requests are generally transmitted to LU Awith an address that includes a specific device identifier, an offsetwithin the device, and a data size. Offsets are generally aligned to 512byte blocks. The average size of a write operation issued by hostcomputer 104 may be, for example, 10 kilobytes (KB); i.e., 20 blocks.For an I/O rate of 50 megabytes (MB) per second, this corresponds toapproximately 5,000 write transactions per second.

System 100 includes two data protection appliances, a source side DPA112 and a target side DPA 124. A DPA performs various data protectionservices, such as data replication of a storage system, and journalingof I/O requests issued by a host computer to source side storage systemdata. As explained in detail hereinbelow, when acting as a target sideDPA, a DPA may also enable rollback of data to an earlier point in time,and processing of rolled back data at the target site. Each DPA 112 and124 is a computer that includes inter alia one or more conventional CPUsand internal memory.

For additional safety precaution, each DPA is a cluster of suchcomputers. Use of a cluster ensures that if a DPA computer is down, thenthe DPA functionality switches over to another computer. The DPAcomputers within a DPA cluster communicate with one another using atleast one communication link suitable for data transfer via fiberchannel or IP based protocols, or such other transfer protocol. Onecomputer from the DPA cluster serves as the DPA leader. The DPA clusterleader coordinates between the computers in the cluster, and may alsoperform other tasks that require coordination between the computers,such as load balancing.

In the architecture illustrated in FIG. 1, DPA 112 and DPA 124 arestandalone devices integrated within a SAN. Alternatively, each of DPA112 and DPA 124 may be integrated into storage system 108 and storagesystem 120, respectively, or integrated into host computer 104 and hostcomputer 116, respectively. Both DPAs communicate with their respectivehost computers through communication lines such as fiber channels using,for example, SCSI commands.

In accordance with an embodiment of the present invention, DPAs 112 and124 are configured to act as initiators in the SAN; i.e., they can issueI/O requests using, for example, SCSI commands, to access logical unitson their respective storage systems. DPA 112 and DPA 124 are alsoconfigured with the necessary functionality to act as targets; i.e., toreply to I/O requests, such as SCSI commands, issued by other initiatorsin the SAN, including inter alia their respective host computers 104 and116. Being target nodes, DPA 112 and DPA 124 may dynamically expose orremove one or more logical units.

As described hereinabove, Site I and Site II may each behavesimultaneously as a production site and a backup site for differentlogical units. As such, DPA 112 and DPA 124 may each behave as a sourceDPA for some logical units and as a target DPA for other logical units,at the same time.

In accordance with an embodiment of the present invention, host computer104 and host computer 116 include protection agents 144 and 164,respectively. Protection agents 144 and 164 intercept SCSI commandsissued by their respective host computers, via host devices to logicalunits that are accessible to the host computers. In accordance with anembodiment of the present invention, a data protection agent may act onan intercepted SCSI commands issued to a logical unit, in one of thefollowing ways:

-   -   Send the SCSI commands to its intended logical unit.    -   Redirect the SCSI command to another logical unit.    -   Split the SCSI command by sending it first to the respective        DPA. After the DPA returns an acknowledgement, send the SCSI        command to its intended logical unit.    -   Fail a SCSI command by returning an error return code.    -   Delay a SCSI command by not returning an acknowledgement to the        respective host computer.

A protection agent may handle different SCSI commands, differently,according to the type of the command. For example, a SCSI commandinquiring about the size of a certain logical unit may be sent directlyto that logical unit, while a SCSI write command may be split and sentfirst to a DPA associated with the agent. A protection agent may alsochange its behavior for handling SCSI commands, for example as a resultof an instruction received from the DPA.

Specifically, the behavior of a protection agent for a certain hostdevice generally corresponds to the behavior of its associated DPA withrespect to the logical unit of the host device. When a DPA behaves as asource site DPA for a certain logical unit, then during normal course ofoperation, the associated protection agent splits I/O requests issued bya host computer to the host device corresponding to that logical unit.Similarly, when a DPA behaves as a target device for a certain logicalunit, then during normal course of operation, the associated protectionagent fails I/O requests issued by host computer to the host devicecorresponding to that logical unit.

Communication between protection agents and their respective DPAs mayuse any protocol suitable for data transfer within a SAN, such as fiberchannel, or SCSI over fiber channel. The communication may be direct, orvia a logical unit exposed by the DPA. In an embodiment of the presentinvention, protection agents communicate with their respective DPAs bysending SCSI commands over fiber channel.

In an embodiment of the present invention, protection agents 144 and 164are drivers located in their respective host computers 104 and 116.Alternatively, a protection agent may also be located in a fiber channelswitch, or in any other device situated in a data path between a hostcomputer and a storage system. Additionally or alternatively, theprotection agent may be installed as part of the storage array IO stack.In some embodiments the DPA may be installed as a virtual appliance oras a set of processes inside the storage array.

What follows is a detailed description of system behavior under normalproduction mode, and under recovery mode.

In accordance with an embodiment of the present invention, in productionmode DPA 112 acts as a source site DPA for LU A. Thus, protection agent144 is configured to act as a source side protection agent; i.e., as asplitter for host device A. Specifically, protection agent 144replicates SCSI I/O requests. A replicated SCSI I/O request is sent toDPA 112. After receiving an acknowledgement from DPA 124, protectionagent 144 then sends the SCSI I/O request to LU A. Only after receivinga second acknowledgement from storage system 108 may host computer 104initiate another I/O request.

When DPA 112 receives a replicated SCSI write request from dataprotection agent 144, DPA 112 transmits certain I/O informationcharacterizing the write request, packaged as a “write transaction”,over WAN 128 to DPA 124 on the target side, for journaling and forincorporation within target storage system 120.

DPA 112 may send its write transactions to DPA 124 using a variety ofmodes of transmission, including inter alia (i) a synchronous mode, (ii)an asynchronous mode, and (iii) a snapshot mode. In synchronous mode,DPA 112 sends each write transaction to DPA 124, receives back anacknowledgement from DPA 124, and in turns sends an acknowledgement backto protection agent 144. Protection agent 144 waits until receipt ofsuch acknowledgement before sending the SCSI write request to LU A.

In asynchronous mode, DPA 112 sends an acknowledgement to protectionagent 144 upon receipt of each I/O request, before receiving anacknowledgement back from DPA 124.

In snapshot mode, DPA 112 receives several I/O requests and combinesthem into an aggregate “snapshot” of all write activity performed in themultiple I/O requests, and sends the snapshot to DPA 124, for journalingand for incorporation in target storage system 120. In snapshot mode DPA112 also sends an acknowledgement to protection agent 144 upon receiptof each I/O request, before receiving an acknowledgement back from DPA124.

-   -   For the sake of clarity, the ensuing discussion assumes that        information is transmitted at write-by-write granularity.

While in production mode, DPA 124 receives replicated data of LU A fromDPA 112, and performs journaling and writing to storage system 120. Whenapplying write operations to storage system 120, DPA 124 acts as aninitiator, and sends SCSI commands to LU B.

During a recovery mode, DPA 124 undoes the write transactions in thejournal, so as to restore storage system 120 to the state it was at, atan earlier time.

As described hereinabove, in accordance with an embodiment of thepresent invention, LU B is used as a backup of LU A. As such, duringnormal production mode, while data written to LU A by host computer 104is replicated from LU A to LU B, host computer 116 should not be sendingI/O requests to LU B. To prevent such I/O requests from being sent,protection agent 164 acts as a target site protection agent for hostDevice B and fails I/O requests sent from host computer 116 to LU Bthrough host Device B.

In accordance with an embodiment of the present invention, targetstorage system 120 exposes a logical unit 176, referred to as a “journalLU”, for maintaining a history of write transactions made to LU B,referred to as a “journal”. Alternatively, journal LU 176 may be stripedover several logical units, or may reside within all of or a portion ofanother logical unit. DPA 124 includes a journal processor 180 formanaging the journal.

Journal processor 180 functions generally to manage the journal entriesof LU B. Specifically, journal processor 180 (i) enters writetransactions received by DPA 124 from DPA 112 into the journal, bywriting them into the journal LU, (ii) applies the journal transactionsto LU B, and (iii) updates the journal entries in the journal LU withundo information and removes already-applied transactions from thejournal. As described below, with reference to FIGS. 2 and 3A-3D,journal entries include four streams, two of which are written whenwrite transaction are entered into the journal, and two of which arewritten when write transaction are applied and removed from the journal.

Reference is now made to FIG. 2, which is a simplified illustration of awrite transaction 200 for a journal, in accordance with an embodiment ofthe present invention. The journal may be used to provide an adaptor foraccess to storage 120 at the state it was in at any specified point intime. Since the journal contains the “undo” information necessary torollback storage system 120, data that was stored in specific memorylocations at the specified point in time may be obtained by undoingwrite transactions that occurred subsequent to such point in time.

-   -   Write transaction 200 generally includes the following fields:    -   one or more identifiers;    -   a time stamp, which is the date & time at which the transaction        was received by source side DPA 112;    -   a write size, which is the size of the data block;    -   a location in journal LU 176 where the data is entered;    -   a location in LU B where the data is to be written; and    -   the data itself.

Write transaction 200 is transmitted from source side DPA 112 to targetside DPA 124. As shown in FIG. 2, DPA 124 records the write transaction200 in four streams. A first stream, referred to as a DO stream,includes new data for writing in LU B. A second stream, referred to asan DO METADATA stream, includes metadata for the write transaction, suchas an identifier, a date & time, a write size, a beginning address in LUB for writing the new data in, and a pointer to the offset in the dostream where the corresponding data is located. Similarly, a thirdstream, referred to as an UNDO stream, includes old data that wasoverwritten in LU B; and a fourth stream, referred to as an UNDOMETADATA, include an identifier, a date & time, a write size, abeginning address in LU B where data was to be overwritten, and apointer to the offset in the undo stream where the corresponding olddata is located.

In practice each of the four streams holds a plurality of writetransaction data. As write transactions are received dynamically bytarget DPA 124, they are recorded at the end of the DO stream and theend of the DO METADATA stream, prior to committing the transaction.During transaction application, when the various write transactions areapplied to LU B, prior to writing the new DO data into addresses withinthe storage system, the older data currently located in such addressesis recorded into the UNDO stream.

-   -   By recording old data, a journal entry can be used to “undo” a        write transaction. To undo a transaction, old data is read from        the UNDO stream in a reverse order, from the most recent data to        the oldest data, for writing into addresses within LU B. Prior        to writing the UNDO data into these addresses, the newer data        residing in such addresses is recorded in the DO stream.

The journal LU is partitioned into segments with a pre-defined size,such as 1 MB segments, with each segment identified by a counter. Thecollection of such segments forms a segment pool for the four journalingstreams described hereinabove. Each such stream is structured as anordered list of segments, into which the stream data is written, andincludes two pointers—a beginning pointer that points to the firstsegment in the list and an end pointer that points to the last segmentin the list.

According to a write direction for each stream, write transaction datais appended to the stream either at the end, for a forward direction, orat the beginning, for a backward direction. As each write transaction isreceived by DPA 124, its size is checked to determine if it can fitwithin available segments. If not, then one or more segments are chosenfrom the segment pool and appended to the stream's ordered list ofsegments.

Thereafter the DO data is written into the DO stream, and the pointer tothe appropriate first or last segment is updated. Freeing of segments inthe ordered list is performed by simply changing the beginning or theend pointer. Freed segments are returned to the segment pool for re-use.

A journal may be made of any number of streams including less than ormore than 5 streams. Often, based on the speed of the journaling andwhether the back-up is synchronous or a synchronous a fewer or greaternumber of streams may be used.

Initializing a Backup Snapshot on Deduplicated Storage

FIG. 3, FIG. 4, and FIG. 5 depict systems and processes for initializinga backup snapshot on deduplicated storage consistent with an embodimentof the present disclosure. Before deduplicated storage can providecontinuous backup protection, it may be necessary to create an initialbackup snapshot of the source storage system. This initial backupsnapshot may represent the earliest point-in-time backup that may berestored. As changes are made to the source storage system, journalfiles and/or new backups may be updated and/or synthesized to providecontinuous protection. In some embodiments, the initial backup snapshotmay be created by streaming IO's from a storage system scan to a dataprotection appliance, or by taking an initial snapshot of the storagesystem and transmitting the entire snapshot to deduplicated storage.

FIG. 3 depicts a system for creating an initial backup snapshot byscanning a source storage system and streaming IO's to the deduplicatedstorage. Data protection application 300 may comprise journal processor302, and may be in communication with deduplicated storage 304. In anembodiment, deduplicated storage 304 may be target side storage residingat a backup site. Data protection appliance 300 may be similar to dataprotection appliance 112 and/or 124, and may be responsible forstreaming IO's to deduplicated storage 304.

In an embodiment, a source storage system may be scanned and individualoffsets may be streamed to data protection appliance 300. The offsetsstreamed from the scanned system may be referred to as initializationIO's, and may be streamed sequentially to data protection appliance 300.For example, the scanned system may comprise offsets 0, 1, 2, and 3,comprising data A, B, C, and D. The initial scan may start at thebeginning of the system, and transmit offset 0, followed by offset 1, etseq.

As data protection appliance 300 receives the initialization IO's,journal processor 302 may identify the offset data and metadata, and maystream the IO's to metadata journal 306 and/or data journal 308 residingon deduplicated storage 304. Data journal 308 may comprise data storedwithin an offset, and metadata 306 may include metadata associated withthat offset. Metadata could include, for example, an offset identifier,size, write time, and device ID. These journals may then be used tosynthesize a backup snapshot on deduplicated storage 304, as discussedbelow.

In some embodiments, a scanned storage system may operate in a liveenvironment. As a result, applications may be writing to the storageconcurrently with the scan process. If an application writes to alocation that has already been streamed, the journal files andultimately the synthesized snapshot may be out of date. To address thisissue, application IO's may be streamed concurrently with theinitialization IO's if the application IO's are to an offset that hasalready been scanned. For example, consider Table 1:

Time Offset t0 t1 t2 t3 0 A A′ 1 B B′ 2 C 3 D D′

Table 1 depicts four different offsets, denoted as 0, 1, 2, and 3, andfour times, t0, t1, t2, and t3. Letters A, B, C, and D may represent thedata stored at the offsets. Time t0 may represent the offsets as theyexist when the scan begins. These offsets may be streamed to dataprotection appliance 300 sequentially from 0 to 3. At time t1, however,the data at offset 1 is modified by an application from B to B′.Similarly, at t2 the data at offset 3 changes from D to D′, and at t3the data at offset 0 changes from A to A′. If the scan transmits thedata at offset 1 before t1, B′ may be missed since the change occurredafter offset 1 was scanned and B was transmitted. Similarly, if the scanhas not reached offset 3 before t2, only D′ will be transmitted since Dno longer exists. It may therefore be beneficial to transmit applicationIO's to data protection appliance 300 if those IO's write to an offsetthat has already been scanned. If the offset has not been scanned, itmay not be necessary to transmit the application IO's because the changewill be transmitted when the scan reaches that offset.

Turning back to FIG. 3 and with continued reference to Table 1, offsetmetadata journal entries 310 and offset data journal entries 312 depictthe state of metadata journal 306 and data journal 308 after the initialscan is complete. While there are only four offsets on the scannedstorage system, there are six entries in the journal because the data inoffset 0 and 1 was modified by an application after they were scanned.They each therefore have two entries: B and B′. Segment D was modifiedafter the scan began, but before it was reached. Segment D thereforeonly has one entry: D′.

Metadata journal entries 310 and data journal entries 312 may includeall of the data necessary to synthesize a backup snapshot of the scannedstorage system. Data journal entries 312 may contain the actual datafrom the storage system: A, B, B′ C, A′ and D′. Note that data D is notin the data journal 308 since it was modified on the storage systembefore its offset was scanned and transmitted. Metadata journal entries310 may include metadata about the offsets. For example, metadatajournal entries 310 may include an offset identifier, offset length, andwrite time, and volume/device ID. In the present example, metadatajournal entries may include the entries shown in Table 2:

-   -   0. Vol A, offset=0; size=8 kb; time=t0    -   1. Vol A, offset=8 kb; size=8 kb; time=t0    -   2. Vol A, offset=8 kb; size=8 kb; time=t1    -   3. Vol A, offset=16 kb; size=8 kb; time=t0    -   4. Vol A, offset=0; size=8 kb; time=t3    -   5. Vol A, offset=24 kb; size=8 kb; time=t2

Table 2's metadata entries may correspond to the states shown inTable 1. The offset at location 0 may be offset 0, the offset at 8 kbmay be offset 1, the offset at 16 kb may be offset 2, and the offset at24 kb may be offset 3. The subscript of each journal entries 310 alsoidentifies the offset associated with that metadata entry.

Deduplicated storage may use metadata journal 306 and data journal 308to synthesize initial backup snapshot 314. First, metadata journal 306may be queried to identify the most recent data associated with eachoffset. Next, the data may be retrieved from journal data file 308 andsynthesized into backup snapshot 314. In some embodiments, synthesizingthe backup snapshot may comprise creating and/or copying pointers ratherthan copying entire data blocks. This could be, for example, using aproduct such as EMC® DataDomain® Boost™.

For example, once the initial scan is complete, data journal 308includes data A, B, B′, C, A′, and D′. A′ and B′ are the result ofapplication IO's occurring during the scan process, and thereforerepresent the present state of offsets 0 and 1. To create backupsnapshot 314, deduplicated storage may therefore retrieve A′, B′, C, andD′ from the data journal 308 and synthesize them together.

Once initial backup snapshot 314 is synthesized, journal entries 310 and312 may no longer be needed. In an embodiment, they may be removed fromdeduplicated storage 304 in order to conserve space. Alternatively, theymay remain in the journals.

The systems and processes discussed in reference to FIG. 3 enable asystem to create an initial backup snapshot. Once the initial snapshotis created, additional processes may enable continuous data protectionand point-in-time recovery. These processes will now be discussed.

Maintaining Backup Snapshots with Continuous Data Replication

With reference now to FIG. 4, a system and process for maintainingbackups using continuous data replication is discussed. As datasetsincrease in size, backing them up to remote or local backup devicesbecomes increasingly costly and complex. Additionally, traditionalbackup processes may not allow point-in-time recovery since the backupsoccur on a periodic, rather than continuous, basis. The methods andsystems discussed herein provide continuous backup protection as writesare made to a source device, thereby reducing backup cost andcomplexity, and may allowing point-in-time recovery for backed up files.

The system of FIG. 4 includes data protection appliance 400, journalprocessor 402, and deduplicated storage 404. These elements may besubstantially similar to those discussed in reference to FIG. 3.Deduplicated storage 404 may include backup snapshot 414, metadatajournal file 406, and data journal file 408. In an embodiment, backupsnapshot file 414 is synthesized in a manner substantially similar tobackup snapshot 314, and may be created using metadata journal entries410 and data journal entries 412.

As users, applications, and other processes access and use the sourcestorage system, data on that system may change and/or new data may becreated. As a result, initial backup snapshot 414 may become stale. Ifthe source storage system should fail, there is a chance that any new ormodified data may be lost. To address this concern, data protectionappliance 400 may receive and stream application IO's to deduplicatedstorage system 404 on a continuous basis, even after initial backupsnapshot 414 is synthesized. Streaming the application IO's allows thebackups on deduplicated storage 404 to remain up-to-date, withoutneeding to perform additional backups of large datasets. This may reducenetwork traffic, reduce workloads, and conserve space on deduplicatedstorage 404.

For example, new metadata entries 411 and new data journal entries 413represent IO's made after initial backup snapshot 414 was synthesized.These entries may be written to metadata journal 406 and data journal408, as shown in FIG. 4, or they may be written to separate journalfiles. In FIG. 4, data A′ and C were modified on the source storagedevice, and the journal entries therefore comprise A″ and C′.

Periodically, new backup snapshots may be synthesized from a previousbackup snapshot and new journal entries. For example, second backupsnapshot 416 may be synthesized from initial backup snapshot 414, newmetadata journal entries 411, and new data journal entries 413. Secondbackup snapshot 416 may be used to restore source storage system up tothe point-in-time the last journal entry was received. In other words,backup snapshot 416 represents a backup of the source storage system ata later timestamp than initial backup snapshot 414.

In an embodiment, synthesizing second backup journal entry 416 may besubstantially similar to synthesizing the initial backup snapshot 414.Rather than synthesizing all of the data from data journal 408, however,unchanged data may be synthesized from initial backup snapshot 414. Inan embodiment, this synthesis may comprise copying and/or creating adata pointer. For example, in FIG. 4 the solid arrows between initialbackup snapshot 414 and second backup snapshot 416 represent unchangeddata that is common between the two. In this case, only B′ and D′ remainunchanged. The dashed arrows represent new or changed data that needs tobe synthesized into second backup snapshot 416. In FIG. 4, A′ is changedto A″, C is change to C′. Synthesizing the data into second backupsnapshot 616 therefore results in A″, B′, C′, D′.

Additionally or alternatively, second backup snapshot 416 may besynthesized entirely from journal entries. Rather than synthesizingunchanged data from initial backup 414, deduplicated storage 404 mayretrieve the unchanged data from data journal entries 412. For example,B′ and D′ may be synthesized from data journal entries 412 rather thanfrom initial backup snapshot 414.

Additional backup snapshots, such as second backup snapshot 416, may becreated periodically or on demand. For example, a user policy mayspecify that new snapshots should be created every week. Additionally oralternatively, a user may be preparing to perform some risky operationson the source storage system, and may demand that a snapshot be createdin case something goes wrong. These policies may be maintained andapplied using data protection appliance 400, deduplicated storage 404,and/or an external system.

The system and processes discussed herein may enable additional backupsnapshots to be synthesized from journal entries and existing snapshots.In some embodiments, the journal entries may be application IO's whichare continuously streamed to a data protection appliance. While thesesnapshots may provide additional data protection, they may only allowdata that exists in the snapshots to be recovered. Combining snapshotsand journal files may, however, allow any point-in-time recovery.

Alignment Fixing for Continuous Replication into Deduplicated Storage

As discussed in the preceding paragraphs and related applications,continuously streaming IO's to a data protection system may providenumerous performance and/or data protection benefits. These IO's may beused to synthesize backup snapshots on the deduplicated storage, whichmay then be used for data recovery. The performance benefits may belessened, however, if the IO's are not properly aligned with the blockson the deduplicated storage. Unaligned IO's may cause data moves duringthe synthesis process rather than mere pointer manipulation. Further, ifIO's are unaligned early in a journal file they may have a cascadingeffect on subsequent IO's. The systems and processes discussed hereinallow a system to align IO's with the deduplicated block sizes.

Synthesis processes, as discussed at least in reference to FIG. 4, allowbackup snapshots to be created with little or no data movement. Reducingdata movement is desirable as it may decrease the likelihood ofduplication, thereby conserving space, and reduce processing time.Rather than moving data, synthesis processes attempt to create pointersto the data as it exists within other files on the system. If a pointercan not be created for the data, the data must be read from the locationwhere it already exists and written to the new file being synthesized.This results in two IO operations, a read and a write, which wouldotherwise be unnecessary.

Unaligned IO's increase the probability of data movement during thesynthesis process. Pointers must themselves be aligned, which means theycan only point to an offset which is a multiple of a data block size,where the data length is also a multiple of the block size. They cannot,for example, point to a location in the middle of the data block.Therefore, if an IO has an offset and/or a data length that is notaligned (i.e. a multiple of) a data block size, the synthesis processcannot create a pointer for that IO and a data move may be necessary.

For example, a deduplicated storage system may have a basic block sizeof 8 kb. Pointers may therefor be created for any data with an offsetand length that is a multiple of 8 kb (e.g offset 24 kb; length 64 kb).Suppose an IO arrives, however, which has a length of 2 kb. No matterwhere this IO is written, a pointer cannot be used because the IO lengthis not a multiple of a block size. As a result, a synthesis processinvolving that IO would need to read and write the 2 kb of data,resulting in two IO operations rather than mere pointer manipulation.

Similarly, if an IO arrives with an offset of 2 kb and a length of 8 kb,the synthesis process cannot use pointer manipulation since the offsetis not a multiple of the block size. As a result, the 8 kb must be readand written to a new location during the synthesis process.

Finally, suppose an IO arrives with an offset of 2 kb and a size of 24kb. This IO may span four separate data blocks. The first 6 kb of the IOwould need to be read/written during the synthesis process since itstarts at 2 kb and has a length of 6 kb, neither of which is a multipleof the 8 kb block size. Similarly, the last 2 kb would need to beread/written since 2 kb is not a multiple of the block size. The middle16 kb, however, may be synthesized using pointer manipulation. Thisportion of the IO may start at offset 8 kb (since the first portionstarted at 2 kb and has a length of 6 kb), and has a total length of 16kb. Both the offset and the length are multiple of the block size, andtherefore do not need to be read or written. As a result, synthesizing afile using this IO would involve both pointer manipulation and IOoperations.

Since IO's are journaled sequentially, the misalignment of a single IOmay have a cascading effect on the rest of the journal. A misaligned IOat the start of a journal file may impact all the subsequent IO's in thejournal, even if they would otherwise be aligned. Suppose, for example,the following IO's arrive at a data protection appliance:

-   -   0. offset=8 kb; size=16 kb    -   1. offset=2 kb; size=2 kb    -   2. offset=24 kb; size=64 kb

Further suppose these offsets are sequentially journaled in a datajournal on deduplicated storage as follows:

-   -   0. offset=0 kb; size=16 kb    -   1. offset=16 kb; size=2 kb    -   2. offset=18 kb; size=64 kb

Note that offsets in the data journal are those for the deduplicatedstorage. The offsets that arrived from the primary storage system (i.e.8 kb, 2 kb, and 24 kb) are stored in the metadata journal.

In the above example, the only IO that is properly aligned in thejournal is the one at offset 0 kb (still assuming a block size of 8 kb).The IO at offset 16 kb is not properly aligned since its length is only2 kb. Further, the IO at offset 16 kb misaligns the next IO, whichstarts at offset 18 kb. As a result, any synthesis operations involvingthese three IOs will require data movement.

With this understanding, FIG. 5, FIG. 6, and FIG. 7 depict processes foraligning the IOs on the deduplicated storage. The alignment process mayoccur at one of multiple locations, or it may be spread across severallocations. In one embodiment, the IOs may be aligned before they aretransmitted to the data protection appliance. Additionally oralternatively, the may be aligned after they arrived. The followingdiscussion addresses several of these embodiments.

FIG. 5 depicts a process for aligning the IOs prior to transmitting themto a data protection appliance and/or deduplicated storage device. Atblock 500, an IO comprising a write request may be received by a storagesystem. In some embodiments, this storage system may be a SAN and the IOmay be received from a host device. Additionally or alternatively, thestorage system may be internal storage on a host device, such as a harddrive.

At block 502, a determination is made whether the IO is aligned with astorage block on a backup storage system. This determination may bemade, for example, by the storage system. In some embodiments, thebackup storage system may be a deduplicated storage, a data protectionappliance, or a combination of both. The next few blocks discuss how thealignment determination is made.

At 504, a block size for the storage block is determined. The storagesystem may already know this block size, or it may request the blocksize from the backup storage system. For example, the block size may be8 kb as discussed above. It should be appreciated that while 8 kb isused as an example, any block size is consistent with any embodimentsdiscussed in this disclosure. For example, the block size could be 2 kb,4 kb, 8 kb, 16 kb, or any other number.

At block 506, an IO offset and an IO size may be determined from the IO.For example, the IO offset may be 2 kb and the IO size may be 2 kb. Thismeans the IO is requesting to write 2 kb of data, starting at offset 2kb. In an embodiment, the write has already been made to the system andthe IO is being processed prior to transmission to the backup storagesystem.

At block 508, a check is made to determine whether the IO offset is amultiple of the block size. If the offset is not a multiple of the blocksize, the IO is not properly aligned (as discussed above).

At block 510, the system attempts to fix the alignment issue.Specifically, the IO offset is changed so that it is a multiple of theblock size. A start offset which is a multiple of the block size isidentified. This start offset may be an offset lower than the IO offset,and in an embodiment is the nearest lower offset that is a multiple ofthe block size. For example, if the IO offset is 2 kb and the data blocksize is 8 kb, the start offset may be 0 kb. Similarly, if the IO offsetis 26 kb and the data block size is 8 kb, the start offset may be 24 kb(or any other lower offset that is a multiple of 8 kb).

At 512, the IO is aligned by changing the IO offset to be the start IO.This process may involve not only changing the offset, but also readingthe data between the new offset and the original IO offset and adding itto the IO. For example, if the IO was to offset 2 kb with a length of 2kb, and the IO offset is changed to 0 kb, the data between 0 kb and 2 kbmay be read and added to the IO. The IO now has an offset of 0 kb and alength of 4 kb. The data includes the original 2 kb to be written to thestorage system, and an additional 2 kb read from the storage system.

At block 514, a check is made to determine whether the IO size is amultiple of the block size. If it is not, the IO is not properlyaligned. Continuing with the example above, an IO may have an offset of0 kb and a length of 4 kb. While the offset is proper, the length isstill not a multiple of the block size. If this IO were transmitted tothe backup storage system it may end up in a data journal file and anysubsequent IOs would be misaligned (since they would start at offset 4kb, which is not a multiple of 8 kb).

Note that in this embodiment the IO size is checked after the offset isaligned. In other words, the IO size is 4 kb, not 2 kb as originallyreceived. This is because an IO size may be a multiple of the block sizewhen the IO arrives, but the size may change after the offset ischanged. Consider an original received IO with an offset of 2 kb and asize of 16 kb. 16 kb is a multiple of a the block size. When the offsetis changed to 0 kb, however, the IO size increases to 18 kb, which isnot a multiple of the block size. If this IO were transmitted to thestorage system, the IO would still not be properly aligned since thefirst block would contain 8 kb and the second block would only contain 2kb.

At block 516, the IO is further aligned by increasing its size to amultiple of the block size. For example, the IO size may be increasefrom 4 kb to 8 kb. The data between 4 kb and 8 kb may be read from thestorage system and added to the IO.

In our example, the original IO with an offset of 2 kb and a length of 2kb now has an offset of 0 kb with a length of 8 kb. It is thereforeproperly aligned with the data block. Additionally, the first 2 kb andthe last 4 kb may comprise data read from the storage system, while thesecond 2 kb may comprise the data to be written to the storage system.

Finally, at block 518 the aligned IO may be transmitted to the backupstorage system for protection. For example, the IO may be transmitted toa data protection appliance and/or the deduplicated storage. Once thesystem receives the IO, no further processing may be necessary since itis properly aligned.

While the process above discusses modifying both the IO offset and theIO size to align the IO, it may not be necessary to perform one or bothof these operations. For example, if the IO offset and IO size are bothmultiples of the block size when the IO arrives, the IO is alreadyaligned and no further operations may be necessary. Further, if the IOoffset is a multiple of the block size, but the IO size is not, only theIO size may need to be modified.

Turning now to FIG. 6, a process is shown for aligning IOs after theyarrive at a data protected system. For example, this alignment processmay occur at a data protection appliance, such as data protectionappliance 400, or a deduplicated storage, such as deduplicated storage404.

At block 600, an IO may be received. This IO may comprise a write to astorage system, and in an embodiment may be received at a dataprotection appliance. In some embodiments, the IO may be received aspart of a continuous data protection process as discussed above and inthe cross referenced applications.

At 602, a determination is made whether the IO is aligned with a storagesystem block in a backup storage system. The backup storage system couldbe, for example, a deduplicated storage system. At least some of thefollowing blocks discuss how this determination is made.

At block 604, a block size is determined. For example, a data protectionappliance may query the backup storage system for the appropriate blocksize. Alternatively, the data protection appliance may already know theappropriate block size. As noted above, this block size could be, forexample, 8 kb—though any other block size is consistent with thisdisclosure.

At block 606, an IO offset and an IO size may be determined from the IO.The IO could have, for example, and IO offset of 2 kb and a size of 2kb. In other words, the IO wishes write 2 kb to the storage device,starting at offset 2 kb.

At 608, a check is made to determine whether the IO offset is a multipleof the block size. If the offset is not a multiple of the block size,the IO is not aligned. This is substantially similar to the examplesgiven above.

At block 610, the IO offset is rounded down to a start offset when theIO offset is not a multiple of the block size. For example, if theoffset is 2 kb and the data block size is 8 kb, the IO offset may berounded down to a multiple of the block size. In this instance, the newoffset would be 0 kb. The new offset may be any offset that is amultiple of the block size and is less than the IO offset, and in someembodiments is the nearest offset that meets those criteria. However,the nearest offset does not necessarily need to be used. For example, ifthe IO offset is 26 kb, it may be rounded down to a start offset of 0kb, 8 kb, 16 kb, or 24 kb.

At 612, the difference between the start offset and the original IOoffset is padded. For example, if the IO offset was 2 kb and the startoffset is 0 kb (rounded down from 2 kb), the difference between 0 kb and2 kb may be padded. In an embodiment, the difference is padded withzeroes. The IO may now have a “start” offset at 0 kb and a length of 4kb, the first 2 kb of which are padded (typically with zeroes).

At block 614, a check may be made to determine whether the IO size is amultiple of the block size. This may be substantially similar to theprocesses discussed above, and a data protection appliance, adeduplicated storage, or some other system may perform the check. If theIO size is not a multiple of the block size, the IO is determined to beunaligned and the alignment process continues.

At block 616, the IO is padded to increase the IO size to a multiple ofthe block size. Continuing with the example above, the IO may have a newstart offset at 0 kb and a total length of 4 kb. The end of the IO,following the data spanning from 2 kb to 4 kb, may be padded to bringthe IO size up to 8 kb, which is a multiple of the block size. As withthe offset size, the IO may be padded to any multiple of the block size(e.g. 8 kb, 16 kb, 24 kb, etc).

In an embodiment, once the IO is properly aligned with the padding(either before or after the actual data) it may be written to thededuplicated storage. In an embodiment, the padded data is written to adata journal and the offsets and other data may be written to a metadatajournal. The data may not, however, be ready to use for recovery. Thisis because the data may not accurately represent the state of thestorage system. Since the IO was padded, the journaled IO may onlycontain a subset of the data actually stored in the storage system. Inour example, the journal will indicate offset 0 kb comprises 2 kb ofpadding, followed by 2 kb of data, followed by another 4 kb of padding.In reality, offset 0 kb likely contains 8 kb of data, only two of whichwere communicated in the IO.

Block 618 may resolve the data discrepancy. At block 618, a read requestis sent to the storage device. In an embodiment, the read request may bea request for data within the padded portions of the IO. In our example,the read request may be for the data between 0 kb and 2 kb, and between4 kb and 8 kb. Additionally or alternatively, the read request may befor the entire 8 kb from 0 kb to 8 kb, including the 2 kb that wasreceived in the original IO. Once the data is received in response tothe request, the data journal entry may be updated in include thecomplete data rather than just the padded data. Additionally oralternatively, nothing may be written to the data journal until the fulldata is received.

To further illustrate the process, including the rereading the unalignedIOs, consider a received IO with an offset of 20 kb and a length of 5kb. Rounding this IO up and down, we end up with an aligned IO spanning16 kb, which will be stored in two 8 kb blocks. The first block willinclude data from offset 16 kb (rounded down from 20 kb) with a lengthof 8 kb. The first 4 kb will be padded and the final 4 kb will containdata. The second block will include data from offset 24 kb with a lengthof 8 kb. The first 1 kb will be data, and the remaining 7 kb will bepadding. The system may then send read requests for the data at offset16 kb, length 16 kb, and update the journal entries accordingly.

As a final example, consider a large IO to offset 6 kb with a length of24 kb. Assuming 8 kb blocks, the IO will be rounded down to 0 kb and thelength will be rounded up to 32 kb. The data associated with the IO willtherefore span four 8 kb blocks. Note that after padding, however, onlythe two blocks on the end (i.e. offset 0 and offset 32) contain paddeddata. The inner blocks do not include any padded data, and thereforenothing needs to be re-read from the storage system. As a result, theread request(s) may only be for offset 0, length 8, and offset 32,length 8.

Turning now to FIG. 7, a synchronization process is discussed. Since thesystem may be a continuous data protection system, new IOs may continueto arrive throughout the alignment process. If an IO makes a write to alocation that is currently being read for alignment purposes, the dataon the backup system be become desynchronized. FIG. 7 addresses thisconcern.

At block 700, an IO comprising a write to a storage device is received.This may be substantially similar to block 600, discussed above.

At block 702, a determination is made whether the IO is aligned with astorage block on a backup system. Again, this process may besubstantially similar to that discussed above.

At 704, any IO that is not aligned may be tracked. For example, the IOmay be tracked in the memory of the data protection system. Thealignment process may continue for tracked IO's, but following thealignment the read request may not be immediately transmitted to thestorage system.

At block 706, the data protection appliance may wait for a host to flushany open IOs to the storage device. For example, the host may be similarto host 104, and the IOs may be managed by source side protection agent144. The data protection appliance may wait until all IOs are flushedfrom the source side protection agent to the storage. This wait mayensure that any data read from the storage is up-to-date.

At block 708, the read requests may be sent to the storage device. Theseread requests may be for aligned IO's, and may be substantially similarto those discussed above.

At block 710, a second IO may be received from the host. For example,the IO may be received at that data protection appliance from the sourceside protection agent. This IO may be received since IOs arecontinuously streamed to the data protection appliance, as discussedabove. In some embodiments, the second IO may be received before theread request is sent at block 708.

At 712, a determination is made whether the second IO comprises a writeto data requested by the read request. In other words, a check is madeto see if this write was for data related to an IO the system is tryingto align (i.e. an IO being tracked). If it is, the tracked IO is dirty.If a read request has been sent, the response may be disregarded.

Finally, at block 714 the dirty IO may restart the alignment process. Inan embodiment, the alignment process is started from the beginning (e.g.from block 602). Alternatively, a new read request may be sent ratherthan starting completely anew. In some embodiments, the dirty IO maysimply be dropped, and no further alignment and/or journaling may occur.

The processes discussed herein enable IO alignment for continuous dataprotection on deduplicated storage. They may decrease space consumptionand increase efficiency both during the journaling process, and duringsnapshot synthesis. Specifically, they may decrease the amount of datamovement during synthesis be enabling more pointer manipulation.

General Purpose Computer System

FIG. 8 depicts a computer system which may be used to implementdifferent embodiments discussed herein. General purpose computer 800 mayinclude processor 802, memory 804, and system IO controller 806, all ofwhich may be in communication over system bus 808. In an embodiment,processor 802 may be a central processing unit (“CPU”) or acceleratedprocessing unit (“APU”). Some embodiments may comprise multipleprocessors, or a processor with multiple cores. Processor 802 and memory804 may together execute a computer process, such as the processesdescribed herein.

System IO controller 806 may be in communication with display 810, inputdevice 812, non-transitory computer readable storage medium 814, and/ornetwork 816. Display 810 may be any computer display, such as a monitor,a smart phone screen, or wearable electronics and/or it may be an inputdevice such as a touch screen. Input device 812 may be a keyboard,mouse, track-pad, camera, microphone, or the like, and storage medium814 may comprise a hard drive, flash drive, solid state drive, magnetictape, magnetic disk, optical disk, or any other computer readable and/orwritable medium. Storage device 814 may also reside inside generalpurpose computer 800, rather than outside as shown in FIG. 1.

Network 816 may be any computer network, such as a local area network(“LAN”), wide area network (“WAN”) such as the internet, a corporateintranet, a metropolitan area network (“MAN”), a storage area network(“SAN”), a cellular network, a personal area network (PAN), or anycombination thereof. Further, network 816 may be either wired orwireless or any combination thereof, and may provide input to or receiveoutput from IO controller 806. In an embodiment, network 816 may be incommunication with one or more network connected devices 818, such asanother general purpose computer, smart phone, PDA, storage device,tablet computer, or any other device capable of connecting to a network.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present implementations are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

For the sake of clarity, the processes and methods herein have beenillustrated with a specific flow, but it should be understood that othersequences may be possible and that some may be performed in parallel,without departing from the spirit of the invention. Additionally, stepsmay be subdivided or combined. As disclosed herein, software written inaccordance with the present invention may be stored in some form ofcomputer-readable medium, such as memory or CD-ROM, or transmitted overa network, and executed by a processor.

All references cited herein are intended to be incorporated byreference. Although the present invention has been described above interms of specific embodiments, it is anticipated that alterations andmodifications to this invention will no doubt become apparent to thoseskilled in the art and may be practiced within the scope and equivalentsof the appended claims. More than one computer may be used, such as byusing multiple computers in a parallel or load-sharing arrangement ordistributing tasks across multiple computers such that, as a whole, theyperform the functions of the components identified herein; i.e. theytake the place of a single computer. Various functions described abovemay be performed by a single process or groups of processes, on a singlecomputer or distributed over several computers. Processes may invokeother processes to handle certain tasks. A single storage device may beused, or several may be used to take the place of a single storagedevice. The disclosed embodiments are illustrative and not restrictive,and the invention is not to be limited to the details given herein.There are many alternative ways of implementing the invention. It istherefore intended that the disclosure and following claims beinterpreted as covering all such alterations and modifications as fallwithin the true spirit and scope of the invention.

What is claimed is:
 1. A method for IO alignment, comprising: receivingan IO comprising a write to a storage device, wherein the IO includesdata journal entries to store on a journal data file and metadataentries to store on a metadata journal file on a deduplicated storage;determining that the data journal entries in the IO are not aligned witha storage block on the deduplicated storage; aligning the IO with thestorage block after determining that the IO and the storage block arenot aligned by providing a primary storage offset for the IO that alignsthe IO with the storage block; writing the data journal entries to thestorage block in the journal data file; storing the primary storageoffset in the metadata journal file apart from the data journal entriesin the journal data file; and synthesizing backup snapshots that includepointers to the data journal entries in prior snapshots and the datajournal entries representing changes to the data journal entries in theprior snapshots after the prior snapshots were synthesized; wherein thealigning of the IO prevents data journal entries movements duringsynthesizing of the backup snapshots and the backup snapshots arelogical units identified by logical unit numbers on the deduplicatedstorage.
 2. The method of claim 1, further comprising: determining ablock size for the storage block; and determining the primary storageoffset from an IO size and the block size for the storage block.
 3. Themethod of claim 2, further comprising determining the IO is not alignedwith the storage block when the IO offset is not a multiple of the blocksize.
 4. The method of claim 3, further comprising rounding the IOoffset down to a start offset, wherein the start offset is a multiple ofthe block size.
 5. The method of claim 4, further comprising padding adifference between the start offset and the IO offset.
 6. The method ofclaim 4, further comprising sending a read request to the storagedevice, the read request comprising a request for data at the startoffset.
 7. The method of claim 4, wherein the start offset is a nearestlower offset that is a multiple of the block size.
 8. The method ofclaim 2, further comprising determining the IO is not aligned with thestorage block when the IO size is not a multiple of the block size. 9.The method of claim 8, further comprising padding the IO to a new IOsize, wherein the new IO size is a multiple of the block size.
 10. Themethod of claim 9, further comprising sending a read request to thestorage device, the read request comprising a request for data on thestorage device within the new IO size.
 11. The method of claim 1,further comprising tracking the IO when it is not aligned with thestorage block.
 12. The method of claim 11, further comprising waitingfor a host to flush an open IO to the storage device.
 13. The method ofclaim 12, further comprising sending a read request to the storagedevice.
 14. The method of claim 13, further comprising receiving asecond IO from the host.
 15. The method of claim 14, further comprisingdetermining whether the second IO comprises a write to a read datarequested by the read request.
 16. A computer program product foralignment, the computer program product comprising a non-transitorycomputer readable medium encoded with computer executable program, thecode enabling: receiving an IO comprising a write to a storage device,wherein the IO includes data journal entries to store on a journal datafile and metadata entries to store on a metadata journal file on adeduplicated storage; determining that the data journal entries in theIO are not aligned with a storage block on the deduplicated storage;aligning the IO with the storage block after determining that the IO andthe storage block are not aligned by providing a primary storage offsetfor the IO that aligns the IO with the storage block; writing the datajournal entries to the storage block in the journal data file; storingthe primary storage offset in the metadata journal file apart from thedata journal entries in the journal data file; and synthesizing backupsnapshots that include pointers to the data journal entries in priorsnapshots and the data journal entries representing changes to the datajournal entries in the prior snapshots after the prior snapshots weresynthesized; wherein the aligning of the IO prevents data journalentries movements during synthesizing of the backup snapshots and thebackup snapshots are logical units identified by logical unit numbers onthe deduplicated storage.
 17. A system for alignment comprising a memoryand a processor, the processor configured to execute instructionscomprising: receiving an IO comprising a write to a storage device,wherein the IO includes data journal entries to store on a journal datafile and metadata entries to store on a metadata journal file on adeduplicated storage; determining that the data journal entries in theIO are not aligned with a storage block on the deduplicated storage;aligning the IO with the storage block after determining that the IO andthe storage block are not aligned by providing a primary storage offsetfor the IO that aligns the IO with the storage block; writing the datajournal entries to the storage block in the journal data file; storingthe primary storage offset in the metadata journal file apart from thedata journal entries in the journal data file; and synthesizing backupsnapshots that include pointers to the data journal entries in priorsnapshots and the data journal entries representing changes to the datajournal entries in the prior snapshots after the prior snapshots weresynthesized; wherein the aligning of the IO prevents data journalentries movements during synthesizing of the backup snapshots and thebackup snapshots are logical units identified by logical unit numbers onthe deduplicated storage.